“It depends on who you talk to,” a prominent curator of photography told me when I asked him to name the world’s top ten photography collectors.

He was right. I asked 20 prominent dealers, auctioneers, collectors, museum directors, and curators. No one had the same list. A further survey produced a consensus, as well as comments on other major topics in the photography world.

“I have not seen anything like it,” Sandra Phillips, curator of photography at the San Francisco Museum of Modern Art, told a reporter recently. She was talking about Pier 24, a 28,000-square-foot gallery that was created last year by Andrew Pilara, a San Francisco investment banker, in an old warehouse in San Francisco that displays the collection of the Pilara Foundation, which he established. Pilara is on the list of Top Ten.

Pier 24 houses about 2,000 photographs, including works by Diane Arbus, Garry Winogrand, Edward Burtynsky, Lee Friedlander, Robert Adams, Hiroshi Sugimoto, Dorothea Lange, Richard Misrach, and many others. Admission is free, and the space is open to the public Monday through Thursday by appointment only.

Pier 24 recently presented an exhibition of the collection of Randi and Bob Fisher, who are also on the Top Ten. Bob Fisher’s parents founded Gap Inc. Among the artists in the show were Edward Weston, Robert Frank, Walker Evans, Paul Strand, Alfred Stieglitz, and Andreas Gursky. Other exhibitions are being planned for Pier 24.

Another topic being discussed is the increasingly global nature of the market, with great depth in France, England, Germany, Italy, Switzerland, Russia, the Middle East, and elsewhere.

Unlike the contemporary art market, there is less speculation and less buying for investment with photography, according to several observers. Collectors are mainly buying because they experience the works and want to live with them.

Other observers point out that more and more collectors of contemporary art are collecting photography, including Eli Broad, who is on the ARTnews list of Top Ten art collectors and has bought many works by Cindy Sherman and Jeff Wall, among others. “Is Eli a photo collector? No,” said one curator. “Does he have a lot of photos? Yes.”

A photography auctioneer said, “We see more and more clients of other departments—Impressionist, modern, contemporary, and American painting —becoming interested in buying photography, whereas 15 years ago they would not.”

The Top Ten for photography also includes Thomas Walther, who has been collecting photography for more than 30 years. In 2001 the Museum of Modern Art acquired—it was a partial gift, partial purchase—328 works by most of the leading European and American photographers of the 1920s and ’30s. The list included Man Ray, Edward Steichen, Stieglitz, Paul Strand, Manuel Bravo, Paul Outerbridge, Berenice Abbott, and many others.

In 2000 the Metropolitan Museum presented the exhibition “Other Pictures: Vernacular Photographs from the Thomas Walther Collection.” Dating from the 1910s through the ’60s, the photos were by anonymous amateurs and were discovered in flea markets, in shoeboxes, or in family albums.